The overall purpose of the Molecular Biology Core (Core C) is to provide efficient shared access to basic molecular biology services for investigators for need to apply a variety of molecular techniques to problems involving HIV replication, pathogenesis, therapy, and immunoprophylaxis of HIV infection, with particular emphasis on support of developmental projects. Specific objectives of Core C include: [1] To provide small and large- scale, cost efficient DNA sequencing for CFAR laboratories, [2] To provide accurate message analysis services to core members, [3] To manage a plasmid library, providing large scale preparation of full-length HIV-1 and HIV-2 viral clones, and [4] To manage a PCR primer library for the efficient distribution of primers shared among investigators. Ongoing Molecular Biology Core support of UCSD research efforts clearly illustrates its need and usefulness. Large sequencing efforts supported include sequencing of Coccididiomycosis inmitis, Aspergillus fumigatus, and Toxoplasma gondii, envelope fragments from pediatric and adult CNS sources ongoing analysis pol mutations induced by treatment with protease inhibitors, and analysis of sequence variation in an HIV-2 M. nemestrina vaccine model. Such efforts are crucial to our understanding of viral resistance, and the meaning of viral variation. The recent introduction of quantitative RT PCR assays for chemokine receptor and beta-chemokine messages by Core C has supported research on HIV induced apoptosis, differential co-receptor usage by HIV strains, the role of co-receptors in nef action, and the use of chemokine receptors by other lentiviruses. The Molecular Biology Core plasmid library has facilitated early work on DNA vaccines for HIV, investigation of nef enhancement of infectivity, determination of HIV genes which contribute to apoptosis, work on bacterial vectors for AIDS vaccines. Primers designed by the core have proven valuable to the construction of new and very useful reporter cell lines bearing CCR5 receptors. The proposed Molecular Biology Core (Core C) represents an extension of a model service core which has been thoroughly tested and proven to be a productive, cost-efficient and useful core resource in the existing UCSD Center for AIDS Research.